The former French prime minister Dominique de Villepin has returned to the thick of Parisian politics, launching a new party and vowing to unite the population around a "republic of solidarity".

In the latest stage of his attempted emergence from the political desert, the debonair career diplomat attempted to capitalise on the defeat of Nicolas Sarkozy's party at the ballot box last weekend by announcing plans for a new "movement" to rival the president's right-wing UMP.

"I have decided to create a political movement – a free and independent movement – open to everyone, whatever their origins, their leanings or their commitments, [which goes] beyond partisan divisions," he told a packed room of journalists and supporters.

"The watchword of my battle is that of a united republic. I do not have a miracle cure, but I believe in France," he said, beating the drum of Gaullist rhetoric and thumbing his nose at Sarkozy's "scattergun" reformist strategy.

De Villepin, who acted as foreign, interior and then prime minister during the presidency of Jacques Chirac, his political mentor, was left isolated when his arch foe became president in 2007. But he has been progressively moving back into the spotlight since last year, when he launched the supporters' network Club Villepin.

In January his comeback was given a significant boost when a Paris court cleared him of any involvement in the Clearstream affair, a legal battle that had pitted him against Sarkozy. Newly exonerated, the poet-cum-politician has since made no secret of his desire to give France an "alternative" political project.

Today, as he trumpeted the new and as yet nameless party, De Villepin refused to speak explicitly of the 2012 presidential election, insisting he was not showcasing "a personal ambition" but a "vision" for the country. Some did not believe that pitch. "Of course it is not the time to talk of candidacies, but of course it is the presidential election which is being aimed at," said Francois Goulard, one of a handful of Villepinistes within the UMP.

For now, and even after the official inauguration of his party on 19 June, De Villepin is expected to focus on building on the rumblings of discontent that led to a bruising defeat for the UMP in regional elections last weekend.

Endorsing a state-friendly brand of conservatism, he made a clear play to exploit the growing feeling that Sarkozy is out of touch with the needs of ordinary people, criticising a 50% tax ceiling and questioning the purpose of public service cuts.

At the Elysée, whose chief resident once reportedly promised to hang De Villepin "by a butcher's hook", reaction to the launch was one of studied indifference. Observers point out De Villepin has little in the way of financial backing or openly stated support. Most importantly, they add, he has never in his 30-year career been elected to political office.

After what has arguably been the worst fortnight of his presidency, Sarkozy looks more vulnerable than ever before. His woes are partly caused by disquiet among the rightwing rank and file.

He refuses to entertain the idea that his loathed rival could be considered a serious opponent, but his appointment to the cabinet on Monday of Georges Tron, a vocal Villepiniste, was interpreted as an attempt to neutralise the threat of a bellicose faction within his party.